Q: My yard has over the years been invaded by this clover. It spreads perhaps via bulbs or tubers. Either way, it is spreading everywhere.

Any ideas how to get rid of it? It's very intrusive.

– Kathy Kaw, Sacramento

A: According to UC Master Gardener Bill Pierce, your weed that resembles clover is Oxalis pes-caprae or Bermuda buttercup, a native of South Africa. It reaches 1 foot high and spreads indefinitely by bulbs.

Digging out the bulbs is the most positive form of control. Pulling off the tops early in the season will eventually destroy the bulb after two or three years of this treatment as it will run out of energy.

Smothering the plants with a thick layer of newspaper or mulch may also help.

"Strong solutions of glyphosate – 3 to 4 ounces of 41 to 50 percent concentrate to a gallon of water – has eliminated it for me," Pierce said.

Glyphosate – the main ingredient in the popular herbicide Roundup – will kill any green plant, so it has to be used with care.

One way to keep the spray off desirable plants is to use a 1-gallon plastic jug that has had the bottom removed.

Place the jug over the plant to be eliminated and enter the wand of your spray unit into the mouth of the jug and then spray.

Q: I have a gardenia plant that is being stripped. I took a sample to Capitol Nursery, but they could not give me any definitive information about what's damaging these plants.

I have used snail bait and Tree and Shrub Insect Control (Imidacloprid) as recommended by Capital Nursery. Can you give me your thoughts?

– James F. Bellotti, Sacramento

A: Your gardenias are being chewed on by black vine weevils, according to UC Master Gardener Bill Pierce.

Adults are black, brown or grayish "snout beetles," about a half-inch long. The larvae are white grubs with brown heads.

Besides gardenias, they attack other woody landscape plants such as azalea, rhododendron, euonymus and liquidambar. The adults attack foliage while the larvae feed on roots.

Adults and offspring live in the soil and the flightless adults climb up stems to feed at night.

Identification of the beetle is necessary before insecticide application.

The imidacloprid you used will kill the adults, but it is not affecting the eggs or grubs. You need to drench the soil around the roots of the plants to eliminate everything.

Malathion is the easiest insecticide to use; for each plant, make 1 or 2 gallons of solution, using the proportions given on the bottle for insect control, and carefully pour it around the plant's root zone.

The insecticide will not harm the gardenias and you may need to drench a second time if the damage continues.

GARDEN QUESTIONS?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties.

Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h&g@sacbee.com. Please put "Garden Detective" in the subject field and include your postal address. To contact your UC Extension directly, call:

• Sacramento: (916) 875-6913; 9 a.m.-noon and 1-4 p.m. weekdays

• Amador: (209) 223-6838; 10 a.m.-noon Monday through Thursday; email ceamador.ucdavis.edu

• Butte: (530) 538-7201; 8 a.m.-noon and 1-5 p.m. weekdays

• El Dorado: (530) 621-5512; 9 a.m.-noon weekdays

• Placer: (530) 889-7388; 9 a.m.-noon on Tuesdays, Wednesday and Thursdays or leave a message and calls will be returned

• Nevada: (530) 273-0919; 9 a.m.-noon Tuesdays through Thursday or leave a message

• Shasta, Tehama, Trinity: (530) 225-4605

• Solano: (707) 784-1322; leave a message and calls will be returned

• Sutter, Yuba: (530) 822-7515; 9 a.m.-noon Mondays and Tuesdays and 1-4 p.m. Thursdays

• Yolo: (530) 666-8737; 9-11 a.m. Tuesdays and Fridays, or leave a message and calls will be returned

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